In recent years, it has been known that a bypass surgery in which the upper part of the stomach and the lower part of the small intestine are surgically directly connected to each other is effective as a method for treating diabetes (especially type 2 diabetes) and obesity. When such a bypass surgery is performed, the nutrients directly flow into the lower part of the intestine from the upper part of the stomach, and the nutrients therefore do not flow to the duodenum and the upper part of the jejunum both located on the upper part of the small intestine. As a result, it is possible to reduce the absorption of nutrients. Further, when the nutrients do not flow to the upper part of the small intestine, glucose-dependent insulinotropic polypeptide (GIP), glucagon and the like which are gastrointestinal hormones secreted in response to the stimulus of nutrients are not likely to be secreted. In addition, when the undigested nutrients pass through the lower part of the jejunum and the ileum both located on the lower part of the small intestine, the secretion of glucagon-like peptide-1 (GLP-1) which is a gastrointestinal hormone increases in response to the stimulus of the nutrients. GIP and glucagon are considered as factors which reduce the secretion of insulin. Therefore, when GIP and glucagon are not secreted, it becomes difficult to inhibit the secretion of insulin. Further, GLP-1 is considered a factor which accelerates the secretion of insulin. As described above, a bypass surgery is considered to exhibit an effect on the treatment of diabetes and obesity not only by restricting the absorption of nutrients, but also by accelerating the secretion of insulin by the action of the gastrointestinal hormone.
However, a bypass surgery is highly invasive. Therefore, in recent years, a low-invasive method in which a sleeve through which nutrients flow is placed on the upper part of the small intestine has been attracting attention. For example, a device provided with a tubular sleeve which can be placed inside the small intestine is described in Japanese Application Publication No. 2010-502289. The device can be orally placed and therefore has low invasiveness. Nutrients which have reached the pyloric ring are allowed to pass through the inside of the sleeve, so that the nutrients can reach the lower part of the small intestine without making contact with the upper part of the small intestine.
In such a device, an increase and decrease of nutrients absorbed by the small intestine depend on the length of the sleeve. Therefore, when reducing the efficiency of digestion and abruption of nutrients by the device after the sleeve is placed inside the small intestine, that is, when increasing the effect obtained by the device, the length of the sleeve may be adjusted to be longer.